In grinding machines, it is necessary to support a grinding wheel on a rotatable machine spindle. The grinding wheel is most often carried on a spindle diameter which fits closely within a central bore in the wheel, and the end faces of the grinding wheel are clamped between a spindle flange and a separate clamping flange which is adapted to be secured to the spindle by a nut, or a plurality of screws, for example. The load which is impressed on the grinding wheel faces by the spindle flange and the clamping flange gives rise to a frictional grip by the flanges on the wheel for torque transmission.
For relatively thin grinding wheels, any changes in wheel width and/or the supporting spindle length in the wheel bore, which may be experienced because of thermal excursions, does not appreciably affect the clamping force exerted by the flanges. However, when a relatively wide grinding wheel is employed, for example, as often encountered in centerless grinding art, which may be in the nature of twenty inches or so, the thermal changes experienced by the supporting grinding wheel spindle may result in such dimensional changes as to appreciably affect the clamping force. If a wheel were put on a cold spindle and clamped to the proper load, as the spindle temperature reaches steady state running conditions, thermal growth of the spindle may tend to lessen the clamping forces on the grinding wheel.
By way of example, a wheel spindle made of steel, has a thermal coefficient of expansion of 6 .times. 10.sup.-6 inches per inch of length per degree Fahrenheit, and, for a 20 inch spindle length at a 30.degree. F temperature change, the spindle change in length would calculate to be 0.0036 inches.
Load on the wheel faces is conventionally obtained by tightening the screws to the same torque reading with a torque wrench, the assumption being that the torque is directly proportional to axial load on the screw. While theoretically so, an actual assembly includes variable elements which are manifested in the torque reading, such as tightness of the thread fit. A better way to indicate axial clamping force is to measure axial position of a clamping member. Accordingly, a gaging ring has been provided in the design of the wheel clamping device of the within invention to measure axial position of the clamping member to correspond to a predetermined axial force.
Therefore, to obviate the difficulties inherent in the prior art, a wheel clamping device is provided, suitable for application to a wheel supporting spindle, which will accomodate certain changes in wheel width and/or spindle length without appreciably affecting the clamping force on the wheel.
It is therefore an object of the present invention to provide a wheel clamping device which will accomodate changes in wheel width and/or spindle length without appreciably affecting the wheel clamping forces.
Another object of the present invention is to provide a wheel clamping device which is capable of being easily installed and readily gaged as to proper load.
Still another object of the present invention is to provide a wheel clamping device which is non-dependent on a torque wrench for proper load.